Ancient cave to which enchantress is reduced (5)
I believe the answer is:
antre
'ancient cave' is the definition.
(archaic term for a cave)
'which enchantress is reduced' is the wordplay.
'is reduced' indicates the answer is hidden within the clue (reducing the letters in the clue shows the answer).
'ANTRE' is hidden in the letters of 'which enchantress'.
'to' acts as a link.
(Other definitions for antre that I've seen before include "Formerly, a cavern" , "Cave used by poets" .)